/* ****************************************************************** **
**    OpenSees - Open System for Earthquake Engineering Simulation    **
**          Pacific Earthquake Engineering Research Center            **
**                                                                    **
**                                                                    **
** (C) Copyright 1999, The Regents of the University of California    **
** All Rights Reserved.                                               **
**                                                                    **
** Commercial use of this program without express permission of the   **
** University of California, Berkeley, is strictly prohibited.  See   **
** file 'COPYRIGHT'  in main directory for information on usage and   **
** redistribution,  and for a DISCLAIMER OF ALL WARRANTIES.           **
**                                                                    **
** Developed by:                                                      **
**   Frank McKenna (fmckenna@ce.berkeley.edu)                         **
**   Gregory L. Fenves (fenves@ce.berkeley.edu)                       **
**   Filip C. Filippou (filippou@ce.berkeley.edu)                     **
**                                                                    **
** ****************************************************************** */

// Written: User-defined implementation for GPU-accelerated formUnbalance
// Purpose: This file contains a simplified implementation of GPU_FormUnbalance.

#include "GPU_FormUnbalance.h"
#include <AnalysisModel.h>
#include <LinearSOE.h>
#include <FE_Element.h>
#include <DOF_Group.h>
#include <Node.h>
#include <Element.h>
#include <Vector.h>
#include <ID.h>
#include <Domain.h>
#include <OPS_Globals.h>

#ifdef USE_CUDA
// Real CUDA implementation would go here
#else
// Non-CUDA stub implementation
GPU_FormUnbalance::GPU_FormUnbalance(int maxEle, int maxDOF, int maxNode) 
    : maxElements(maxEle), maxDOFs(maxDOF), maxNodes(maxNode),
      currentElements(0), currentDOFs(0), currentNodes(0),
      profilingEnabled(false), lastComputeTime(0.0), lastTransferTime(0.0)
{
    // Initialize empty structures when CUDA is not available
    memset(&gpuData, 0, sizeof(GPUData));
    memset(&streams, 0, sizeof(GPUStreams));
}

GPU_FormUnbalance::~GPU_FormUnbalance()
{
    // Nothing to clean up in non-CUDA version
}

int GPU_FormUnbalance::formUnbalance(AnalysisModel* theAnalysisModel, LinearSOE* theSOE)
{
    if (theAnalysisModel == 0 || theSOE == 0) {
        opserr << "GPU_FormUnbalance::formUnbalance - ";
        opserr << "no AnalysisModel or LinearSOE has been set\n";
        return -1;
    }

    // CPU fallback implementation
    // Zero the matrix
    theSOE->zeroA();
    
    // Process the elements
    FE_Element* elePtr;
    FE_EleIter& theEles = theAnalysisModel->getFEs();
    while ((elePtr = theEles()) != 0) {
        elePtr->zeroTangent();
        elePtr->addKtToTang();
        if (theSOE->addA(elePtr->getTangent(), elePtr->getID()) < 0) {
            opserr << "GPU_FormUnbalance::formUnbalance - failed to addA\n";
            return -1;
        }
    }
    
    // Process the DOF groups
    DOF_Group* dofPtr;
    DOF_GrpIter& theDOFs = theAnalysisModel->getDOFs();
    while ((dofPtr = theDOFs()) != 0) {
        if (theSOE->addA(dofPtr->getTangent(), dofPtr->getID()) < 0) {
            opserr << "GPU_FormUnbalance::formUnbalance - failed to addA\n";
            return -1;
        }
    }
    
    // Form the unbalance vector
    theSOE->zeroB();
    
    // Process elements again for unbalance
    theEles.reset();
    while ((elePtr = theEles()) != 0) {
        if (theSOE->addB(elePtr->getResidual(), elePtr->getID()) < 0) {
            opserr << "GPU_FormUnbalance::formUnbalance - failed to addB\n";
            return -1;
        }
    }
    
    // Process DOF groups again for unbalance
    theDOFs.reset();
    while ((dofPtr = theDOFs()) != 0) {
        if (theSOE->addB(dofPtr->getUnbalance(), dofPtr->getID()) < 0) {
            opserr << "GPU_FormUnbalance::formUnbalance - failed to addB\n";
            return -1;
        }
    }
    
    return 0;
}

// Stub methods for non-CUDA implementation
int GPU_FormUnbalance::initializeGPU() { return 0; }
void GPU_FormUnbalance::cleanupGPU() {}
int GPU_FormUnbalance::transferDataToGPU(AnalysisModel* theAnalysisModel) { return 0; }
int GPU_FormUnbalance::transferResultFromGPU(LinearSOE* theSOE) { return 0; }
int GPU_FormUnbalance::computeElementResidualsGPU() { return 0; }
int GPU_FormUnbalance::computeNodalUnbalanceGPU() { return 0; }
int GPU_FormUnbalance::assembleGlobalResidualGPU() { return 0; }
int GPU_FormUnbalance::updateElementData(AnalysisModel* theAnalysisModel) { return 0; }
int GPU_FormUnbalance::updateNodalData(AnalysisModel* theAnalysisModel) { return 0; }
bool GPU_FormUnbalance::checkGPUError(const char* operation) { return true; }
int GPU_FormUnbalance::allocateGPUMemory() { return 0; }
void GPU_FormUnbalance::freeGPUMemory() {}
int GPU_FormUnbalance::reallocateIfNeeded(int newElements, int newDOFs, int newNodes) { return 0; }

// CUDA kernel stubs
extern "C" {
    void launch_computeElementResiduals(
        const double* d_coords, const int* d_connectivity, const int* d_types,
        const double* d_properties, const double* d_displacements,
        const int* d_dofMaps, double* d_residuals,
        int numElements, int maxNodesPerElement, int maxDOFsPerElement,
        cudaStream_t stream) {}
    
    void launch_computeNodalUnbalance(
        const double* d_nodalLoads, const int* d_nodalDOFMaps,
        double* d_globalResidual, int numNodes, int maxDOFsPerNode,
        cudaStream_t stream) {}
    
    void launch_assembleGlobalResidual(
        const double* d_elementResiduals, const int* d_assemblyIndices,
        const int* d_assemblyOffsets, double* d_globalResidual,
        int numElements, int maxDOFsPerElement, cudaStream_t stream) {}
}
#endif // USE_CUDA 